Effect of CeO2 and Y2O3 as Catalysts on Hydrogen Desorption Properties of NaAlH4

The effect of two rare earth oxides (0, 0.5, 1, 2, 3, 4, 5 mol% CeO2 and 0, 0.5, 1, 2, 3, 4 mol% Y2O3) on hydrogen desorption of NaAlH4 by mechanical milling under an atmosphere of argon was studied. The PCT result reveals that increasing content of CeO2 and Y2O3 causes a similar effect trends on the maximum dehydrogenation amount and the dehydrogenation rate which increases firstly and then decreases under the same moderate conditions. CeO2 as the catalyst for NaAlH4 presents superior catalytic activity to Y2O3. For the same amount of 4.8 wt%, the dehydrogenation rate of that of 1 mol% CeO2-NaAlH4 is obviously faster than that of 1 mol% Y2O3-NaAlH4. SEM analysis shows that with the increasing of catalyst content, the microscopic surface morphology of all the samples changes from homogeneous to flocculent. Besides, the dispersive particle structure may have a bigger reaction area than the flocculent structure and heating could make NaAlH4 form a kind of porous structure like honeycomb.